Apparatus for grinding and polishing cylindrical lenses



Nov. 12, 1935. A. J. HOLMAN 2,020,312

' APPARATUS FOR GRINDINGAND POLISHING GYLINDRICAL LENSES Filed Feb 8,1930 5 Sheets-Sheet 1 NQv. 12, 1935. A. J. HOLMAN 2,020,312

APPARATUS FOR GRINDING AND POLiSHING CYLINDRICAL LENSES Filed Feb 8,1930 s sheets-sheet 2 Nov. 12, 1935. A. J. HOLMAN APPARATUS FOR GRINDINGAND POLISHING CYLINDRICAL LENSES Filed Feb. 8, 1930 :s sheets sheet'sjve7z ar I I, v a WA 1", I 722:5 207 Patented Nov. 12, 1935 UNITEDSTATES NT OFFICE A APPARATUS FOR GRINDING AND POLISH- ING CYLINDRICALLENSES Claims.

My invention relates to means for grinding and: polishing concavecylindrical surfaces in lenses,. and it has been. the special object ofmy invention to provide a simple apparatus which 5. will function withprecision. so as to produce a truly cylindrical. surface.

My device may be best understood by reference to the accompanyingdrawings in which.

Fig. l is a plan view of my device with bearlO ing brackets for thesliding carriage partly broken away to show the means for supporting thecarriage.

Fig. 2 is a front view showing the method of shifting. the linkconnections for oscillating the lap when. a cylinder of short radius isto be ground.

Fig. 3; is a plan view of the lens chuck and lens centering andvpositioning ring- Fig.4 is a plan view of the lens centering andpositioning ring.

Fig. 5 is aside view of my device.

Fig- 6- is a cross section. on line 66 of Fig. 3 of the lens chuck andlens centering and positioning ring;

5 Referring now more. specifically to the drawings, I is the main framewhich may be suitably attached to the bench. 2;. Bolted to the backwallv 3 of the mainv frame I is a bracket 4 which has integral.therewith bearing brackets 5 and 6,

3 wherein is mounted the crankshaft l, and bearing brackets 8 and 9(Fig. 2) wherein is mounted the drive" shaft ll). The bracket 4 alsocarries a bearing bracket H which supports one end of. the crank shaft[2,. the other end of which 35; isjournaled in the: bearing bracket l3which is bolted to the main frame Ir.

The crankshaft I carries a. crank block M to which is attached in anadjustable manner the crank pin I5. A gear Hi is fast mounted on crankshaft 1 and meshes with a gear ll fast mounted on: drive. shaft II].which carries also a drive pulley l8, and. a helical gear I!) whichmeshes with a helical gear 20 on crank shaft [2. Thrust bearing 21 onshaft I0; and thrust bearing. 22 on shaft [:2 carry the end thrustresulting from the interaction. ofthe. helicalv gears I9 and 2D.

A. crank block 23 is mounted on crank shaft l2 and carries-theadjustably mountedv crank pin 2d.

Bolted tothe top of the main frame I are parallel. bearing brackets 25and 26 in which are slidablymounted rods 21 and 28 to which is attachedthe cross member 29. A connecting rod 391 mounted on. crank pin l-5enters a recess 55: in the cross member 2-9. andv is hingedly attachedthereto by means of the pin 3| fixed in the lugs 32 and 33 whichare-integral with the cross member 29.

A chuck carrier 34 is hingedly connected to bosses 35 and 36, which areintegral with cross 5 member 29, by the hinge pins 3-1 and 38 fastmounted respectively in said bosses 35 and 36.

A bar 39, which is rectangular in cross section,

is fixedly mounted at one end in a boss 40 integral with the chuckcarrier 34, being retained 10 in position by the pin M. The bar 39 isalso secured in a slot in a. rib 42' on the chuck carrier 34 by means-ofthe cap-plated? which is attached by screws 44 and 45 to said rib. Thebar 39' may drop into close fitting engagement with the 15 slotted topof the bracket 46 which: is attached to the main frame I by'bolts. 41'and 48.

A dependent arm 49 having a flanged top 50 is secured by bolts 51 and52' to the bottom of the main frame I. an integral rib 53 havingthereina row of tapped holes 54 inany one of which may be screwed thebolt 55 which passes through a slot in the base of the bracket 56 andretains the bracket in the desired position. of vertical. adjustment.The 25 bracket 56' has a forked end 51 wherein is. hingedly mounted onpin 58 the bracket 59 which is adjustably secured to the oscillating arm60 by means of the bolt 6| which passes through a slot in the base ofthe bracket 59 and enters one 3.0 of the tapped holes 62 in rib 63 onthe oscillating arm 60.

The upper end 64' (Fig; 5') of the oscillating arm til is flangedtosupport-the lap tray 65 which is secured thereto by screws 66. Withinthe lap 3.5 tray 65 is secured the'cylindrical lap 61. Mounted betweenbolts M and 48 which enter the main frame I is an arched guide bar 68which has. a. close sliding fit within a slot in the upper end of theoscillating arm 6|]. A connecting rod 69 40 is connected at one end tothe crank pin 24 and at the other end is hinged on the pin- 70 which isfixed in the upper portion of the oscillation arm 60.

To more easily actuate ,the oscillating arm 60 45 when the device isadjusted for cylinders of short radius by an extreme elevation of thebrackets 56 and 59, the connecting rod 69 may be disconnected from pinl0- and connected to' the pin H which is mounted on a rocking. bracket12 50 pivoted on a pin 13 fixed on the arm 49. A link 1A, is thenemployed to connect the oscillating arm 50 and the rocking bracket 12,being attached by pin l5 fixed in the arm 6!] and by pin 16 fixed in theswinging bracket 12. 55

This arm 49- is provided with 20 The lens 11 to be ground is mounted andpositioned in the chuck I8 in the following manner: The lens is placedupon a warming plate, the face to be ground being placed against thewarming plate and the ring I9 is then placed about the lens TI. Thisring I9 is of a thickness substantially equal to that of the part of thelens which is to project from thechuck I8 when mounted therein, and theinternal diameter of the ring I9 is such as to permit it to fit closelyabout the lens II. Four rectangular bosses 80 project from the uppersurface of the ring I9, their inner faces being located symmetricallywith respect to the center of said ring. The chuck I8 has fourprojecting bosses8l, the outer faces of which are located symmetricallywith respect to the center of the chuck I8 and are spaced so as to fitwithin the bosses 80 on the ring I9 (Figs. 3 and 6) Hence when thecavity of the chuck I8 is coated with pitch 82 and the chuck is presseddown upon the ring I9 which contains the lens 11, the lens will becentered and squared in said chuck. A slow application of heat willcause the pitch to adhere to the lens and after cooling, the ring I9 maybe removed, and the chuck I8 bearing the lens TI is now ready formounting in the grinder.

To maintain the chuck I8 in proper position in the grinding machine, Ihave provided a pair of diametrically opposite pins 83 thereon and on adiameter at right angles thereto, I have provided a pair of rectangularslotted bosses 84. The chuck carrier 34 is provided with a pair ofoppositely placed dependent slotted lugs 85 which will closely embracethe pins 83 on the chuck I8. As the hingedly mounted chuck carrier 34 isdropped into position over the chuck I8, the bar 39 enters the slots inthe bosses 84 and so aligns the chuck that the slotted lugs 85 willembrace the pins 33 when the chuck is moved longitudinally into theproper position.

Before proceeding to grind a lens thus mounted in the machine a lap ofthe desired curvature has been, of course, selected and mounted in themachine in the manner heretofore described. The brackets 56 and 59 areso positioned with respect to the lap that the axis of the pin 58coincides with the axis of the cylindrical surface of the lap. Hencewhen the oscillating arm is rocked the lap surface will oscillate aboutits own axis of ourvature and retain its true contour and impart a likecontour to the surface of the lens being ground.

An examination of Figs. 1, 2, and 5, will show that the slidably mountedcross member 29, the chuck carrier 34, which is hinged thereto by thehinge pins 3! and 38, the rectangular bar 39 rigidly attached to thechuck carrier 34 and fitting into the slotted top of the bracket 46, andthe "slotted lugs 85 (integral with the chuck carrier 34) which embracethe pins 83 on the chuck I8, are all designed and arrange-d to preventany and all movement of the lens 11 in a direction tangential to thecylindrical surface of the lap 61. Thus the lens IT has no freedom ofmotion except that of translation along a straight path parallel to theaxis of the abrading surface of the lap. However, as the glass is groundaway by the abrading action, the lens Il is free to feed radiallydownward toward the axis of the cylindrical surface, due to the hingeaction at the pins 83, which permits the top of the lens chuck 8 toremain always parallel to its initial position.

It will also be observed that the pin 58 centered on the axis of thecylindrical surface of the lap 67, and the arched guide bar 68 whichfits closely within a slot in the upper end of the oscillating arm 60,are designed and arranged to constrain the cylindrical surface of thelap to travel only over an extended cylindrical surface which iscoincident with its own cylindrical contour.

ously essential in any device wherein the lens blank is to be restrainedfrom rocking and tilting, and constitutes the feature which ischaracteristic of my device and which distinguishes it from all 10cylindrical grinding mechanisms wherein pivot mounting of the lens blankmust be provided. This movement of the lap causes the abrading surfaceto remain truly cylindrical throughout the grinding operation, and,moreover, it eliminates 15 all tendency for the lens, due to contactwith the moving lap, to move in any direction except tangentially to thelap surface, and, as has already been pointed out, the lens carriagestructures are designed to prevent such tangential motion of 20 thelens. Thus the structures provide constant and exact alignment of theaxis of the lens with respect to the axis of the lap, combined withideally smooth and uniform abrading action, both on the lens blank andon the lap. 25

Thus, my device combines two simple movements; namely, linearreciprocation of the lens and pure oscillation of the lap supportingmember, each of which movements takes place in a plane at right anglesto the other, and the struc- 30 tures are so arranged that neithermoving element can change or in any way affect the motion of the other.The abrading action between lens and lap which results from thecombination of these two simple movements, takes place, as pre- 35viously indicate-d, without periodic rocking, tilting or rotating of thelens, therefore the cylindrical surfaces generated by my device are farmore accurate than the surfaces produced by former cylinder grindingmachines. especially useful in producing large surfaces such as arerequired in certain reflector arc condenser lenses, wherein acylindrical surface having a radius of curvature of 32 inches isrequired to be formed in one face of a condenser lens 8 inches 45 indiameter. Such large cylindrical surfaces must be made very accuratelyto meet the requirements of non-intermittent motion picture projection,and no apparatus heretofore constructed is suitable for producing suchlarge and precise 60 work.

Power applied to the drive pulley I8 will, through gears 11 and I6impart rotation to the crank shaft I and through its attached crankmechanism reciprocate the slidably mounted cross 5% member 29 and thechuck carrier 34 which constitute the lens carriage thereby impartingreciprocating motion to the lens.

The drive shaft I through gears I9 and 20 also rotates crank shaft I2which through the crank 60 mechanism attached thereto, imparts theoscillating movement above described to the lap.

The gear ratios between the power shaft I 0 and the crank shafts I andI2 are such as to impart to the lens carriage and to the lap motions ofdifferent frequencies so that any given point on the lap surface willtravel through devious paths on the lens surface, thus producing avaried pattern to the wiping action and a thorough and uniformdistribution of the grinding mixture. Pressure may be applied to the arm39 as desired to secure the necessary grinding action.

To polish the lens surface after grinding a suitable polishing elementis substituted for the lap above described. This polishing element maybe This 5 particular movement of the lap surface is obvi- Hence mydevice is 40* made of either pitch or felt or a combination of pitch andfelt or other fabric. I recommend as a satisfactory polisher one made upby cementing a felt covering over the surface of the lap and applyingthereto a coating of beeswax. When the polisher is so constituted, it isobvious that the radius of oscillation of the surface of the polisherhas been increased by an amount equal to the thickness of the materialapplied to the lap, and therefore it becomes necessary correspondinglyto lower the oscillating arm 60.

The accuracy of grinding which is obtained by the use of my device issuch that the surface is true to the curvature of the lap andconsequently the polishing is accomplished rapidly and evenly, thusproving the precision with which the grinding and polishing operationsareperformed.

While I have described and illustrated one preferred form of myapparatus for grinding and polishing cylindrical lens surfaces, it willbe obvious to those skilled in the art that other mechanical structuresmay be used to provide the same action; i. e., the oscillating of acylindrical lap about its axis and the reciprocation of a chuck along apath parallel to the axis of said lap, the oscillating and reciprocatingmovements being entirely independent of each other, and the combinedmovements providing an abrading action wherein the lens blank is notrequired to perform periodic rocking, tilting or rotating movements. Theappended claims are drawn with a View to covering any and all apparatussuitable for and/or capable of performing successfully in the mannerabove described.

Having thus fully described my invention, what I claim is:

1. In a device of the character specified, the combination of a slidablymounted lens carriage provided with a hingedly mounted chuck carrieradapted and arranged to hingedly support a chuck, means for impartingreciprocating movement to said lens carriage, a lap oscillatablysupported on an axis parallel to the direction of reciprocation of saidlens carriage, and means for oscillating said lap.

2. In a device of the character specified the combination of a slidablymounted lens carriage provided with a hingedly mounted chuck carrieradapted and arranged to hingedly support a chuck, means for impartingreciprocating'movement to said lens carriage, said chuck carrier beingprovided with an outwardly extending guide bar, a slotted guide memberby which the outer end of said guide bar is aligned, a lap oscillativelysupported on an axis parallel to the direction of reciprocation of saidlens carriage, and means for oscillating said lap.

3. In a device of the character specified the combination of a slidablymounted lens carriage provided with a hingedly mounted chuck carrier, alens chuck, means on said chuck carrier arranged to engage and retainsaid chuck in proper alignment when said hingedly mounted chuck carrieris swung into operative position, means for imparting reciprocatingmovement to said lens carriage, a lap oscillatably supported on an axisparallel to the direction of reciprocation of said lens carriage, andmeans for oscillating said lap.

4. In a device of the character specified the combination of a slidablymounted lens carriage provided with a hingedly mounted chuck carrier, aguide bar mounted on said chuck carrier, said chuck carrier beingprovided with dependent slotted lugs, a lens chuck provided with a pairof diametrically opposite slotted bosses adapted to embrace said guidebar and a pair of diametri cally opposite pins adapted to fit withinsaid dependent slotted lugs thereby hingedly connecting said lens chuckwith said chuck carrier, means for imparting reciprocating movement tosaid lens carriage, a lap oscillatably supported on an axis parallel tothe direction of reciprocation of said lens carriage, and means foroscillating said lap.

5. A lens chuck comprising a disc shaped body hollowed out on one sideto receive a lens blank, four bosses projecting radially from said discshaped body and lying on two diameters intersecting at right angles, theouter faces of said bosses being equidistant from the center of saidchuck, a pair of diametrically opposite pins projecting from two of saidbosses, and a pair of rectangular slotted bosses projecting normallyfrom the fiat face of said disc shaped body, said rectangular slottedbosses being located adjacent the periphery of said chuck and on adiameter at right angles to the axis of said pins.

ARTHUR J. HOLMAN.

